In the field of high-speed printing devices which are especially suitable for use in connection with electronic data processing systems, the wire matrix type of printer has come into increasing use. In this type of printer, letters, numbers and symbols are formed from a series of dots produced by the impact of the ends of a plurality of wire elements on record media, most customarily in combination with an ink ribbon which provides the ink needed to produce a mark on the record medium being printed upon.
One problem which has arisen in connection with use of printers of the wire matrix type is that of fatigue breakage of the print wires and associated springs employed to return the wire to a non-printing position after a printing stroke. This breakage results from bending and vibration of the print wires caused by the high force employed to drive the wires over a short distance to impact upon the record medium being printed upon or the ink ribbon associated therewith. In order to reduce or eliminate such breakage, in some prior art structures, the individual print wires have been confined within print head blocks or units, or within tubes or coil springs anchored in the printer framework. However such structures have the disadvantages of increasing the parts and labor costs, and also tend to impede the movement of the printer wires by frictional engagement between the wires and the tubes. This, in turn, has led in some instances to further structural alterations of the printers to provide means for lubricating the wires within the tubes, thereby additionally increasing the cost and complexity of the assembly.
In another approach to solution of this problem, tubular elements have been placed on the print wires to ride freely thereon and exercise a vibration dampening function, as disclosed and claimed in the co-pending United States patent application Ser. No. 758,521, filed Jan. 11, 1977, inventors Nelson et al., now U.S. Pat. No. 4,060,161, issued Nov. 29, 1977, assigned to the assignee of the present application.